JP2016026138A - Glass composition having high thermal and chemical stability, and production method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a glass for a liquid crystal display substrate, which has a high strain point and good dimensional stability and exhibits chemical characteristics.SOLUTION: An alkali-free glass is provided, which comprises, in terms of mol% on the basis of oxide, 64.0 to 72.0 of SiO, 9.0 to 16.0 of AlO, 1.0 to 5.0 of BO, 1.0 to 7.5 of MgO+LaO, 2.0 to 7.5 of CaO, 1.0 to 7.0 of BaO, and 0.0 to 3.5 of SrO. The glass has such characteristics that: (1) Σ(MgO+CaO+SrO+BaO)/(AlO)≤1.50; (2) when the content of SrO is not 0 mol%, a ratio BaO/SrO is 2.0 or more; (3) any oxides other than SiO, AlO, BO, MgO, CaO, BaO, SrO, and LaOare included by 2.0 mol% or less; and (4) each content of AsOand SbOis 0.005 mol% or less.SELECTED DRAWING: None

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is hereby incorporated by reference in its entirety under US Patent Act (35 USC) of US Provisional Patent Application No. 60 / 772,600, filed February 10, 2006, which is incorporated herein by reference. Insist on the benefits of Article 119 (e).

  The manufacture of liquid crystal displays, for example active matrix liquid crystal displays (AMLCD), is very complex and the properties of the substrate glass are very important. Glass substrates used in the manufacture of AMLCD devices, first and foremost, need to strictly control their physical dimensions. The downdraw sheet stretching process, in particular, the fusion method described in US Pat. Nos. 5,037,086 and 2,029 by Dockerty should be used as a substrate that does not require expensive post-forming finishing operations such as lapping and polishing. Can be produced. Unfortunately, the fusion process places severe limitations on glass properties and requires a relatively high liquidus viscosity.

  In the liquid crystal display field, thin film transistors (TFTs) based on polycrystalline silicon are preferred. This is because it has the ability to carry electrons more efficiently. A polycrystalline silicon transistor (p-Si) is characterized by having higher mobility than an amorphous silicon transistor (a-Si). This allows smaller and faster transistors to be manufactured, ultimately creating a brighter and faster display.

  One problem with p-Si based transistors is that manufacturing requires higher process temperatures than are used in the manufacture of a-Si transistors. These temperatures are in the range of 450 ° C. to 600 ° C. compared to the peak temperature of 350 ° C. used for the manufacture of the a-Si transistor. At these temperatures, most AMLCD glass substrates undergo a process known as consolidation. Consolidation, also called thermal stability or dimensional change, is an irreversible dimensional change (shrinkage) in a glass substrate due to changes in the fictive temperature of the glass. “Virtual temperature” is a concept used to indicate the structural state of glass. Glass that is quenched from high temperatures is said to have a high fictive temperature due to "freezing" in the high temperature structure. Glass that is annealed by slow cooling or holding for some time to near its annealing point is said to have a low fictive temperature.

  The degree of consolidation depends on both the process of making the glass and the viscoelastic properties of the glass. In the float process for producing sheet products from glass, the glass sheet is cooled relatively slowly from the melt and “freezes” the relatively low temperature structure into the glass. In contrast, the fusion process cools the glass sheet from the melt very rapidly and freezes it to a relatively hot structure. As a result, the glass produced by the float process is less consolidated than the glass produced by the fusion process. This is because the driving force for compaction is different between the fictive temperature and the process temperature experienced by the glass during consolidation. Thus, it is desirable to minimize the level of consolidation in a glass substrate manufactured by the downdraw method.

  There are two ways to minimize consolidation in glass. First, the glass is pretreated with heat to provide a fictive temperature similar to that experienced by the glass during p-Si TFT fabrication. However, there are several problems with this method. First, a plurality of slightly different fictive temperatures exist in the glass due to a plurality of heating steps used during the manufacture of the p-Si TFT, and this pretreatment cannot completely compensate for this. Second, the thermal stability of the glass is closely related to the details of p-Si TFT fabrication, that is, the pre-treatment varies from end user to end user. Finally, preprocessing increases processing costs and complexity.

  Another way is to slow down the consolidation response. This is done by increasing the viscosity of the glass. Thus, if the strain point of the glass is much higher than the process temperature it undergoes (eg, if the strain point is about 200-300 ° C. higher than the process temperature after a short exposure), consolidation is minimal. is there. However, a challenge with this method is the production of high strain point glass that is cost effective.

  Described herein are alkali-free glasses having a high strain point and good dimensional stability (ie, low pressure density) and methods for making the same. Furthermore, the glass composition also has all the properties required for downdraw processing, which are important for the manufacture of liquid crystal display substrates.

U.S. Pat. No. 3,338,696 US Pat. No. 3,682,609

  In accordance with the objectives described above, the disclosed materials, compounds, compositions, articles, devices, and methods embodied and broadly described herein are in flat panel display devices, such as active matrix liquid crystal displays (AMLCDs). It is an alkali-free boroaluminosilicate glass that exhibits desired physical and chemical properties for use as a substrate. According to that particular embodiment, the glass has good dimensional stability depending on the strain point. Additional advantages will be set forth in part in the description which follows, and in part will be obvious from the description, and will be found by implementing the embodiments described hereinafter. The advantages described below will be realized and obtained by means of the elements and combinations particularly suggested in the appended claims. Both the foregoing general description and the following detailed description are considered to be illustrative and explanatory and not restrictive.

  The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several aspects described below.

  The materials, compounds, compositions, articles, devices, and methods described herein are readily understood by reference to the following detailed description, examples, and drawings of specific aspects of the disclosed components. .

  Prior to disclosing and describing the materials, compounds, compositions, articles, devices and methods of the present invention, the embodiments described below are not limited to specific synthesis methods or specific reagents (specific batch components), Naturally, it can be changed. Further, the terms used in the present specification are only for describing specific aspects, and are not intended to be limiting. Furthermore, various references are made throughout this specification. The disclosures of these documents are all incorporated by reference into the present application and more fully describe the state of the art related to the disclosed content. The disclosed references are also separately and specifically incorporated by reference with respect to the materials contained therein, which are mentioned in the text on which the reference relies.

  Throughout the description and claims, the word “comprise” and other forms of this wording, such as “comprising” and “comprises” It is not limited and does not exclude these, but includes, for example, other additives, ingredients, integers or steps.

  As used in the description and the appended claims, “a”, “an”, and “the” include the plural unless specifically stated otherwise. Thus, for example, “composition” includes a mixture of two or more such compositions, “solvent” includes a mixture of two or more such solvents, and “layer” includes: Combinations of two or more such layers are included.

  “Any” or “optional” means that the event or situation described below may or may not occur, and the explanation includes when the event or situation occurs and when it does not occur It is.

  Certain materials, compounds, compositions and components disclosed herein can be readily obtained commercially or using techniques generally known to those skilled in the art. For example, starting materials and reagents used to prepare the disclosed compounds and compositions are obtained from commercial suppliers or prepared by methods known to those skilled in the art.

  Also disclosed are materials, compounds, compositions, and ingredients that can be used in, combined with, used in the preparation of, or products of, the disclosed methods and compositions. is there. When these and other materials are disclosed herein, and combinations, subsets, interactions, groups, etc. of these materials are disclosed, each of these compounds is disclosed in various separate and collective ways. Even though combinations and permutations are not explicitly disclosed, each is specifically predicted and considered to be described herein. For example, if a composition is disclosed and a number of modifications can be made to a number of components of the composition, each possible combination and permutation is specifically predicted unless specifically stated otherwise. . Thus, when the classes of components A, B and C are disclosed together with the classes of components D, E and F, and examples of combinations AD are disclosed, each is not listed separately Each is predicted separately and collectively. Thus, in this example, each of the combinations of AE, AF, BD, BE, BF, CD, CE, and CF is specifically predicted. , A, B, and C; D, E, and F are considered to be disclosed, an example combination is AD. Likewise, these subsets or combinations are also specifically predicted and disclosed. Thus, for example, the sub-group of AE, BF, and CE is specifically predicted and considered to be disclosed from the disclosure of A, B, and C; D, E, and F, The combination is AD. This concept applies to all aspects of this disclosure including, but not limited to, steps in methods of making and using the disclosed compositions. Thus, where there are a variety of additional steps that can be performed, each of these additional steps can be performed with a particular aspect or combination of aspects of the disclosed method aspects, each such combination being It is assumed that it was specifically predicted and disclosed.

  As a specific example of the concept of a subset, the range of components of the glass of the present invention (including the total range of components) or the range of properties of these glasses, in particular the range of components or properties recited in the claims, At either the upper or lower limits of the range, it can be narrowed (corrected) to values for the components or characteristics disclosed herein. It does not matter whether the disclosure is the corresponding upper or lower limit of other ranges of components or properties (eg, preferred ranges), the amount of components used in a particular embodiment, or the properties shown in a particular embodiment. With respect to narrowing the claims based on the embodiments, other portions of the embodiments can be narrowed regardless of whether they are within the narrowed claims.

  Reference will now be made in detail to specific embodiments of the disclosed materials, compounds, compositions, articles, and methods, examples of which are illustrated in the accompanying Examples and Figures.

  Described herein are alkali-free glasses having a high strain point and good dimensional stability (ie, low pressure density) and methods for making the same. High strain point glass can prevent panel distortion due to compaction / shrinkage during heat treatment after glass manufacture.

  Glasses with strain points above 700 ° C. are quenched and minimize the dimensional changes (ie, consolidation) experienced by glass that is reheated for a short period of time. In one embodiment, the glass composition described herein has a strain point of 700 ° C. or higher or 710 ° C. or higher. In further embodiments, the glass compositions described herein have a strain point of 700 ° C to 800 ° C, 700 ° C to 775 ° C, 700 ° C to 750 ° C, or 700 ° C to 730 ° C. In a further aspect, the high strain point glass compositions described herein are heat consolidated to less than 30 ppm, less than 25 ppm, less than 20 ppm, less than 15 ppm, or less than 10 ppm after 600 ° C. heat treatment for 5 minutes. Low pressure density is preferred.

  In one aspect, the glasses described herein have a strain point greater than about 700 ° C. and undergo a 30 ppm consolidation (ie, dimensional change) after heat treatment at 600 ° C. for 5 minutes. This temperature and time was chosen to approximate the low temperature polysilicon heat treatment cycle. FIG. 1 shows experimental data for a series of glasses. Strain point measured along the x-axis versus measured dimensional change of 600 ° C. over 5 minutes.

In one aspect, described herein is an alkali-free glass, in mole percent on an oxide basis,
SiO ₂ 64.0-72.0
Al ₂ O ₃ 9.0-16.0
B ₂ O ₃ 1.0-5.0
MgO ₊ La ₂ O 3 1.0-7.5
CaO 2.0-7.5
SrO 0.0-4.5
BaO 1.0-7.0
Where Σ (MgO + CaO + SrO + BaO + 3La ₂ O ₃ ) / (Al ₂ O ₃ ) ≧ 1.15, where Al ₂ O ₃ , MgO, CaO, SrO, BaO and La ₂ O ₃ are each Represents the mole percent of the oxide component.

In a further aspect, described herein is an alkali-free glass, in mole percent on an oxide basis,
SiO ₂ 64.0-72.0
B ₂ O ₃ 1.0-5.0
Al ₂ O ₃ 9.0-16.0
MgO ₊ La ₂ O 3 1.0-7.5
CaO 2.0-7.5
SrO 0.0-4.5
BaO 1.0-7.0
Where, where
(A) 1.15 ≦ Σ (MgO + CaO + SrO + BaO + 3La ₂ O ₃ ) / (Al ₂ O ₃ ) ≦ 1.55, where Al ₂ O ₃ , MgO, CaO, SrO, BaO and La ₂ O ₃ are each Represents the mole percent of the oxide component,
(B) The glass has a strain point of 700 ° C. or higher,
(C) the glass has a viscosity of 200 poise and a temperature of 1,665 ° C. or less;
(D) The glass has a viscosity of 85,000 poise or more at the liquidus temperature.

In other embodiments, described herein is an alkali-free glass, in mole percent on an oxide basis,
SiO ₂ 65.0-71.0
Al ₂ O ₃ 9.0-16.0
B ₂ O ₃ 1.5-4.0
MgO ₊ La ₂ O 3 0.5-7.5
CaO 2.0-6.0
SrO 0.0-4.5
BaO 1.0-7.0
La ₂ O> 0.0 and 4.0 or less, where
Σ (MgO + CaO + SrO + BaO + 3La ₂ O ₃ ) / (Al ₂ O ₃ ) ≧ 1.15 (preferably ≧ 1.2), where Al ₂ O ₃ , MgO, CaO, SrO, BaO and La ₂ O ₃ Represents the mole percent of each oxide component.

In a further aspect, described herein is an alkali-free glass, in mole percent on an oxide basis,
SiO ₂ 65.0-72.0
Al ₂ O ₃ 10.0-15.0
B ₂ O ₃ 1.0-4.0
MgO 2.0-7.5
CaO 3.0-6.0
SrO 0.0-4.5
BaO 1.0-6.0
Where, where
Σ (MgO + CaO + SrO + BaO) / (Al ₂ O ₃ ) ≧ 1.15, where Al ₂ O ₃ , MgO, CaO, SrO and BaO represent the mole percentage of each oxide component.

In a further aspect, described herein is SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO, and an alkali-free glass comprising at least one of SrO and BaO. The glass composition is
[MgO]: [CaO]: [SrO + BaO] = 1 ± 0.15: 1 ± 0.15: 1 ± 0.15 (preferably [MgO]: [CaO]: [SrO + BaO] = 1 ± 0.1 : 1 ± 0.1: 1 ± 0.1)
Where [MgO], [CaO] and [SrO + BaO] are the concentration of the indicated component of the glass in mole percent on an oxide basis. Preferably, in this regard, the B ₂ O ₃ concentration is 4.0 mole percent or less. As shown in the Examples, it has been found that a glass that satisfies the above relationship has a low liquidus temperature (high liquidus viscosity) that is desirable for a downdraw process, for example, a fusion process. As described below, SrO and BaO concentrations can be adjusted to optimize strain point, CTE, and density. The BaO / SrO ratio in mole percent is preferably 2.0 or more.

In the glass composition described herein, SiO ₂ functions as a basic glass former. In certain embodiments, when the concentration of SiO ₂ exceeds 64 mole percent, it has a density and chemical durability suitable for flat panel display glass (eg, AMLCD glass), liquidus temperature (liquidus viscosity). Glass is obtained, and the glass can be formed by a downdraw method (for example, a fusion method). With respect to the upper limit, generally, if the SiO ₂ concentration is about 72.0 mole percent or less, the batch material can be melted using conventional high volume, melting techniques such as Joule melting in a heat resistant melter. . As the SiO ₂ concentration increases, the temperature (melting point) of 200 poise usually increases. In various applications, the SiO ₂ concentration is adjusted so that the melting point of the glass composition is 1,650 ° C. or lower. In one embodiment, SiO ₂ concentration is 66.0 to 71.0 mole percent or 66.5 to 70.5 mole percent.

Al ₂ O ₃ is another glass former used to make the glass described herein. An Al ₂ O ₃ concentration of 9.0 mole percent or higher gives the glass a low liquidus temperature and a corresponding high liquidus viscosity. Using at least 9.0 mole percent Al ₂ O ₃ also improves the strain point and modulus of the glass. To obtain a Σ (MgO + CaO + SrO + BaO + 3La ₂ O ₃ ) / (Al ₂ O ₃ ) ratio of 1.15 or higher (see below), it is desirable to keep the Al ₂ O ₃ concentration below 16.0 mole percent. In one embodiment, _Al 2 _{O 3} concentration is from 12.0 to 15.0 mole percent.

B ₂ O ₃ is both a glass former and a flux that aids melting and lowers the melting point. In order to obtain these effects, the B ₂ O ₃ concentration of the glass composition described in the present specification is 1.0 mole percent or more.

During display processing, glass sheets are often held only at opposite ends. Accordingly, the unsupported central portion of the sheet hangs down. The amount of sag is a function of sheet geometry, density and glass Young's modulus. Sheet geometry depends on the specific process used and is beyond the control of the glass manufacturer. For a fixed density, an increase in Young's modulus is desirable. This is because the drooping amount exhibited by the large glass sheet decreases during transportation, handling and heat treatment. Similarly, in proportion to the increase in Young's modulus, it results in an increase in density or an increase in droop. In one embodiment, the density of the glass is 2.75 grams / cm ³ or less. In another aspect, to minimize the contribution to the droop of the glass itself, the ratio of Young's modulus / density, more than 30.0GPa · ^cm 3 / g, more than 30.5GPa · ^cm 3 / g, exceeds 31.2GPa · ^cm 3 / g, or desirably exceed 32.2GPa · ^cm 3 / g. Higher ratios are preferred. Substituting alkaline earth oxides, La ₂ O ₃ or Al ₂ O ₃ , reduces the density of B ₂ O ₃ but decreases the Young's modulus more rapidly. Thus, it is desirable to keep the B ₂ O ₃ content reasonably low. B ₂ O ₃ also tends to lower the strain point, and for this reason it is preferred to keep the B ₂ O ₃ content of the glass as low as possible.

As described above with respect to SiO _2, in LCD applications, glass durability is also very important. Durability can be controlled slightly by increasing the alkaline earth and lanthanum oxide concentrations and significantly reducing the high content of B ₂ O ₃ . It is desirable to keep the B ₂ O ₃ content low, such as strain point and Young's modulus. Thus, to achieve the above properties, in one aspect, the glass described herein is 5.0 mole percent or less, 1.0-5.0 mole percent, 1.0-4.0. mole percent, has a _B 2 _{O 3} concentration of 2.0 to 4.0 mole percent.

Al ₂ O ₃ and B in order to increase strain point, increase elastic modulus, improve durability, reduce density and reduce coefficient of thermal expansion (CTE) while maintaining glass melting and forming properties _{The 2} O ₃ concentration can be selected as a pair.

For example, an increase in B ₂ O ₃ and a corresponding decrease in Al ₂ O ₃ is useful to obtain low density and CTE, while an increase in Al ₂ O ₃ and a corresponding decrease in B ₂ O ₃ Is useful for increasing the strain point, modulus, and durability. Provided, however, that the increase of _Al 2 _{O 3} is, Σ (MgO + CaO + SrO + BaO) / (Al 2 O 3) or _{Σ (MgO + CaO + SrO +} BaO + 3La 2 O 3) / (Al 2 O 3) not lower than about 1.15 ratio. For example, as is known in the art, the CTE (0-300 ° C.) of glass used in AMLCD applications is 28-42 × 10 ⁻⁷ / ° C., preferably 30-40 × 10 ⁻⁷ / ° C., most The range is preferably 32-38 × 10 ⁻⁷ / ° C. The CTE measured for other temperature ranges, for example, 25 to 300 ° C. as shown in the examples described later, can be converted to a range of 0 to 300 ° C. by correcting the measured values. When converting CTE values measured for the range of 25-300 ° C to values for the range of 0-300 ° C, a correction of -0.8x10 ^-7 / ° C is appropriate for AMLCD silica-based glasses. It has been found to be. With respect to CTE, traditionally lamp glasses have a low boron and high alkaline earth content (leading to a high alkaline earth to alumina ratio), but these glasses are deliberately 42 × 10 ⁻⁷ / ° C. Which has a CTE greater than that which is comparable to molybdenum leads. Accordingly, the lamp glass is not suitable for use in AMLCD applications.

In addition to the glass formers _(SiO 2, _Al 2 _{O 3} and _B 2 _{O 3),} glass described herein also include alkaline earth oxides. In one aspect, at least three alkaline earth oxides, such as MgO, CaO and BaO, and optionally SrO are part of the glass composition. Alkaline earth oxides give the glass various properties that are important for melting, fining, shaping and end use. Accordingly, to improve the glass performance in these respects, in one embodiment, the Σ (MgO + CaO + SrO + BaO) / (Al ₂ O ₃ ) ratio is 1.15 or more, 1.2 or more, or 1.25 or more. In another embodiment, the Σ (MgO + CaO + SrO + BaO) / (Al ₂ O ₃ ) ratio is 1.55 or less and 1.50 or less.

The concentration of MgO, La ₂ O ₃ or combinations thereof in the glass and the Σ (MgO + CaO + SrO + BaO + 3La ₂ O ₃ ) / (Al ₂ O ₃ ) ratio of the glass can affect glass performance, especially meltability and clarity. . Accordingly, in order to improve the glass performance in these respects, in one aspect, the Σ (MgO + CaO + SrO + BaO + 3La ₂ O ₃ ) / (Al ₂ O ₃ ) ratio is 1.15 or more, 1.20 or more, 1.25 or more. . In another embodiment, the Σ (MgO + CaO + SrO + BaO + 3La ₂ O ₃ ) / (Al ₂ O ₃ ) ratio is 1.15 or more, 1.55 or less, 1.25 or more and 1.45 or less.

For certain embodiments of the invention, MgO and La ₂ O ₃ are effectively treated as a single composition component. This is because the effects on viscoelastic properties, liquidus temperature and liquid phase relationship are quantitatively very similar. Other alkaline earth oxides form feldspar minerals, in particular anorthite (CaAl ₂ Si ₂ O ₈ ) and celsian (BaAl ₂ Si ₂ O ₈ ) and this strontium-containing solid solution. Neither MgO nor La ₂ O ₃ is added to these crystals. Therefore, when the feldspar crystals are already in the liquid phase, the addition of MgO or La ₂ O ₃ actually serves to stabilize the liquid relative to the crystals and lower the liquidus temperature. At the same time, the viscosity curve typically becomes steep and lowers the melting point with little or no effect on low temperature viscosity. In this sense, the addition of a small amount of MgO and / or La ₂ O ₃ reduces the melting point, lowers the liquidus temperature, and raises the liquidus viscosity while maintaining the high strain point and low pressure density. The advantage of molding by is obtained.

The effects of MgO and La ₂ O _{3 on} these properties are similar, but the effects on other key glass properties are very different. La ₂ O ₃ greatly increases the density and CTE increases gently compared to MgO. When either is added to the aluminosilicate glass of the present invention, Young's modulus typically increases, but the density rapidly increases with La ₂ O ₃ content, decreasing the specific modulus (Young's modulus divided by density). . To avoid excessive sagging of the sheet during heat treatment, it is desirable to have a specific modulus of at least 28 MPa · m ³ / kg, which is typical for AMLCD substrates. The Young's modulus of the glass of the present invention is about 77.6 to about 83 GPa, and when the density exceeds about 2.75 g / cc, the specific modulus is lower than desired. For this reason, the need to suppress La ₂ O ₃ is not higher than the need to obtain the desired effect on viscoelastic properties. MgO does not have this effect, but at high concentrations it has been found that barium aluminosilicate celsian has a high solubility, and for the liquid phase it remains at a level comparable to La ₂ O ₃ or below. There is a need to.

Increasing the total MgO + La ₂ O ₃ increases the liquidus temperature, and the liquidus viscosity can drop to a level that would be compromised using a high viscosity forming process (eg, a fusion process). Accordingly, the amount of MgO and La ₂ O ₃ can be adjusted to obtain desirable properties for glass formation.

In terms of concentration, when both are present, the combined concentration of MgO + La ₂ O ₃ must be 1.0 to 7.5 mole percent to obtain the various advantages described above. In another embodiment, MgO concentration, in particular, the MgO, when used in _La 2 _{O 3} No is particularly 2.0 to 6.0 mole percent, or 3.0 to 6.0 mole percent. In a further aspect, the La ₂ O ₃ concentration is preferably kept below about 3.0 mole percent so as not to increase the density of the glass.

Calcium oxide present in the glass composition can produce the most desirable ranges of low liquidus temperature (high liquidus viscosity), high strain point and modulus, and CTE for flat panel applications, particularly AMLCD applications. . It is also preferable because it contributes to chemical durability, and is relatively inexpensive as a batch material compared to other alkaline earth oxides. However, at high concentrations, CaO increases density and CTE. Furthermore, if the SiO ₂ concentration is sufficiently low, CaO stabilizes anorthite and the liquidus viscosity decreases. Therefore, in one embodiment, the CaO concentration can be 2.0 mole percent or more. In other embodiments, the CaO concentration of the glass composition is 7.5 mole percent or less, 3.0 to 7.5 mole percent.

  The remaining alkaline earth oxides SrO and BaO both contribute to low liquidus temperature (high liquidus viscosity), and the glasses described herein are typically among these oxides. Contains at least one. However, the selection and concentration of these oxides is selected to eliminate CTE and density increases, and elastic modulus and strain point decreases. The relative proportions of SrO and BaO are balanced so that a suitable combination of physical properties and liquidus viscosity is obtained and the glass can be formed by the downdraw method.

To summarize the effect / role of the central component of the glass of the present invention, SiO ₂ is the basic glass former. Al ₂ O ₃ and B ₂ O ₃ are also glass formers and can be selected as a pair. For example, increasing B ₂ O ₃ used and correspondingly decreasing Al ₂ O ₃ results in low density and CTE, increasing Al ₂ O ₃ used and correspondingly decreasing B ₂ O ₃ . As a result, the strain point, elastic modulus and durability increase. However, even if Al ₂ O ₃ is increased, the RO / (Al ₂ O ₃ ) or (RO + 3La ₂ O ₃ ) / (Al ₂ O ₃ ) ratio is not lowered to less than about 1.15. In the formula, RO = Σ (MgO + CaO + SrO + BaO). If this ratio is too low, the meltability is impaired. That is, the melting point becomes too high. B ₂ O ₃ can lower the melting point by using it, that's _B 2 _{O 3} of high level, the strain point is impaired.

In addition to meltability and strain point considerations, for AMCLD applications, the CTE of the glass must be comparable to silicon. To obtain such a CTE value, the glass of the present invention controls the RO content of the glass (or, RO + _3La 2 _{O 3} content of glass containing _La 2 _{O 3).} For a _Al 2 _{O 3} content, controlling the RO content (for glasses containing the or _{La 2 O 3, (RO +} 3La 2 O 3) / Al 2 O 3 ratio) RO / _Al 2 _{O 3} ratio control Corresponding to. In fact, a glass with a suitable CTE is made when the RO / Al ₂ O ₃ ratio (or (RO + 3La ₂ O ₃ ) / Al ₂ O ₃ ratio) is less than about 1.55.

In addition to these considerations, the glass can preferably be formed by a downdraw method, for example, a fusion method. That is, the liquidus viscosity of the glass needs to be relatively high. Individual alkaline earths play an important role in this regard. This is because the formed crystal phase may be unstable. BaO and SrO are particularly efficient in controlling the liquidus viscosity and are included in the glasses of the present invention at least for this purpose. As shown in the following examples, glasses with high liquidus viscosity are produced by various combinations of alkaline earths. RO / Al ₂ O ₃ ratio (or (RO + 3La ₂ O ₃ ) / Al ₂ required to obtain a low melting point, high strain point, and suitable CTE across alkaline earths (also La ₂ O ₃ when used) It satisfies the limit of O ₃ ratio).

In addition to the components described above, the glass compositions described herein can include various other oxides to adjust various physical, melting, fining, and forming attributes of the glass. Such other oxides include, but are not limited to, TiO ₂ , MnO, Fe ₂ O ₃ , ZnO, Nb ₂ O ₅ , MoO ₃ , Ta ₂ O ₅ , WO ₃ , Y ₂ O ₃ and CeO ₂ is exemplified. In one embodiment, the amount of each of these oxides is 2.0 mole percent or less, and the total combined concentration is 4.0 mole percent or less. The glass compositions described herein also include various contaminants, particularly Fe, associated with batch materials and / or introduced into the glass by melting, fining and / or forming equipment used to make the glass. ₂ O ₃ and ZrO ₂ may also be included. Glass is also a result of the Joule melting using tin oxide electrodes, and / or tin-containing materials, for _example, SnO 2, _SnO, by weighing such SnCO 3, _SnC 2 _{O 4,} possibly containing SnO _2.

Glass compositions are generally free of alkali, but glass can contain some alkaline contaminants. In AMCLD applications, it is desirable to keep the alkali level below 0.1 mole percent so that diffusion of alkali ions from the glass into the silicon of the TFT does not adversely affect thin film transistor (TFT) performance. As used herein, “glass without alkali” is a glass having a total alkali concentration of 0.1 mole percent or less. The total alkali concentration is the sum of Na ₂ O, K ₂ O and Li ₂ O concentrations. In one embodiment, the total alkali concentration is 0.07 mole percent or less.

As described above, clarification, that is, a molten batch of gaseous inclusions, with a ratio of Σ (MgO + CaO + SrO + BaO) / (Al ₂ O ₃ ) and Σ (MgO + CaO + SrO + BaO + 3La ₂ O ₃ ) / (Al ₂ O ₃ ) of 1.15 or more Removal from the material is improved. With this improvement, a clearer package that is more environmentally friendly can be used. For example, on an oxide basis, the glass compositions described herein can have one or more or all of the following composition characteristics.
(I) an As ₂ O ₃ concentration of up to 0.05 mole percent,
(Ii) up to 0.05 mole percent Sb ₂ O ₃ concentration;
(Iii) A maximum of 0.2 mole percent SnO ₂ concentration.

As ₂ O ₃ is an efficient high temperature fining agent for AMLCD glasses, and in certain embodiments described herein, As ₂ O ₃ is used for fining because of its superior fining properties. However, As ₂ O ₃ is toxic and requires special handling in the glass manufacturing process. Therefore, in a specific embodiment, clarification is performed without using a large amount of As ₂ O ₃ . That is, the As ₂ O ₃ of the finished glass is 0.05 mol percent at the maximum. In one embodiment, As ₂ O ₃ is not intentionally used for glass fining. In such cases, the As ₂ O ₃ of the finished glass is at most 0.005 mole percent due to contaminants present in the batch material and / or equipment used to melt the batch material.

Although not as much as As ₂ O ₃ , Sb ₂ O ₃ is also toxic and requires special handling. Furthermore, Sb ₂ O ₃ raises the density, raises the CTE, and lowers the strain point compared to glass using As ₂ O ₃ or SnO ₂ as a fining agent. Therefore, in a specific embodiment, clarification is performed without using a large amount of Sb ₂ O ₃ . That is, Sb ₂ O ₃ of the finished glass is 0.05 mol percent at the maximum. In other embodiments, Sb ₂ O ₃ is not intentionally used for glass fining. In such cases, the Sb ₂ O ₃ of the finished glass is at most 0.005 mole percent due to contaminants present in the batch material and / or equipment used to melt the batch material.

Compared to As ₂ O ₃ and Sb ₂ O ₃ fining, tin fining (ie, SnO ₂ fining) is less efficient, but SnO ₂ is a material that is everywhere no harmful properties are observed. For many years, SnO ₂ has also been a component of AMLCD glass that utilizes tin oxide electrodes in Joule melting of glass batch materials. Even in the presence of SnO _{2 in} AMLCD glasses, no adverse effects using these glasses have been observed in the production of liquid crystal displays. However, high concentrations of SnO ₂ are not preferred. This is because crystal defects can be formed in AMLCD glass. In one embodiment, the finished glass has a SnO ₂ concentration of 0.2 mole percent or less.

Tin fining can be used alone or in combination with other fining techniques as desired. For example, tin fining can be used in combination with halide fining, such as bromine fining. Other possible combinations include, but are not limited to, tin clarification and sulfuric acid, sulfide, cerium oxide, mechanical foaming and / or vacuum clarification. These other clarification techniques are believed to be able to be used alone. In certain embodiments, maintaining the Σ (MgO + CaO + SrO + BaO + 3La ₂ O ₃ ) / (Al ₂ O ₃ ) ratio and the individual alkaline earth and La ₂ O ₃ concentrations within the ranges described above is performed by a clarification process. Make it easier and more efficient.

The glasses described herein can be manufactured using various techniques known in the art. In one aspect, the glass is made using a downdraw method, such as, for example, a fusion downdraw method. In one aspect, described herein is a method of producing an alkali-free glass sheet by a downdraw process that includes batch material selection, melting, and fining steps. The constituting glass contains SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO and BaO, and on an oxide basis,
(I) Σ (MgO + CaO + SrO + BaO) / (Al ₂ O ₃ ) ratio of 1.15 or more,
(Ii) a MgO content of 2.0 mole percent or more,
(Iii) a CaO content greater than or equal to 3.0 mole percent, and (iv) a BaO content greater than or equal to 1.0 mole percent, wherein
(A) Clarification is performed without a large amount of arsenic (optionally without a large amount of antimony),
(B) The average gas content level of an assembly of 50 consecutive glass sheets made from the molten and clarified batch material by the downdraw method is less than 0.10 gas content / cubic centimeter, The volume of the sheet is at least 500 cubic centimeters.

  US Pat. Nos. 5,785,726 (Dorfeld et al.), 6,128,924 (Bang et al.), 5,824,127 (Bang et al.) And co-pending application Ser. No. 11 / 116,669 disclose a process for producing arsenic-free glass.

  In one aspect, the average gas content level of a collection of 50 consecutive glass sheets made from the melted and clarified batch material by a downdraw process is less than 0.05 gas content / cubic centimeter, The volume of each sheet is at least 500 cubic centimeters.

  The downdraw sheet drawing method described in Patent Documents 1 and 2 incorporated by reference, in particular the fusion method, can be used here. Compared to other formation processes such as the float process, the fusion process is preferred for several reasons. First, glass substrates made from the fusion method do not need to be polished. In the present glass substrate polishing, a glass substrate having an average surface roughness measured by atomic force microscopy of about 0.5 nm (Ra) can be produced. The average surface roughness measured by atomic force microscopy of a glass substrate produced by the fusion method is less than 0.5 nm. The substrate also has an average internal stress measured by an optical delay of 150 psi or less.

  In order to form by the down draw method, the liquidus viscosity of the glass composition described in the present specification is desirably 85,000 poise or more, 100,000 poise or more, 150,000 poise or more, and higher. Liquid viscosity is preferred.

Various glass articles can be made using the glass compositions described herein. For example, a liquid crystal display such as AMLCD can be manufactured using the glass composition described in this specification. In one embodiment, the glass described herein has a value of (Young's modulus) / density> 30.5 GPa · cm ³ / g, 5 samples of polished samples, suitable for use in flat panel display applications. Less than 0.8 mg / cm ² weight loss when exposed to% HCl solution at 95 ° C. for 24 hours, 1 volume of 50 wt. % HF and 10 volumes of 40 wt. When exposed to a solution of% NH ₄ F at 30 ° C. for 5 minutes, it has a weight loss of 1.5 mg / cm ² or less.

It shows the dependence on dimensional change and is stated in “consolidation” versus strain point for a series of glass compositions described herein heated at 600 ° C. for 5 minutes. Figure 3 shows consolidation behavior versus time for three glass samples repeatedly heat treated at a temperature of 600 ° C.

  The following examples are set forth below to illustrate the methods and results in accordance with the disclosed configuration requirements. These examples do not include all aspects of the components disclosed herein, but exemplify representative methods and results. These examples are not intended to exclude equivalents and variations of the present invention which are apparent to one skilled in the art.

Efforts have been made to ensure accuracy with respect to numbers (eg, amounts, temperature, etc.) but there may be some errors and deviations. Unless otherwise specified, the temperature is ° C. or ambient temperature, and the pressure is at or near atmospheric pressure. The composition itself is given in mole percent on an oxide basis and is normalized to 100%. There are many variations and combinations of conditions that can be used to optimize reaction conditions, such as component concentrations, temperatures, pressures and other reaction ranges, and product purity and yields obtained from the processes described. Only suitable routine experimentation is required to optimize such process conditions.
Example 1-Preparation of test sample After a test glass sample was prepared by melting a suitable batch material in a Pt crucible at 1,600-1,650 ° C for 6 hours or more and pouring onto a steel sheet, Conventional annealing was performed before cutting and polishing for testing. The resulting putty of glass was processed to obtain a rectangular or square glass sample approximately 3 inches × 7 inches × 2 mm thick or 4 inches × 4 inches × 2 mm thick. Rectangular or square glass was heated to a temperature corresponding to a viscosity of 10 ¹¹ poise, held for 4 hours, and then rapidly cooled to room temperature. This heat treatment is considered to be the best approximation of the thermal history of the fusion draw sheet. The flat surface of the sample is polished and marked with a set of several reference marks near the edges (and perpendicular to the long axis of the sample for rectangular samples). A rectangular sample is cut into half lengths to make one reference part and another part to be heat-treated. The reference piece and the heat treated piece are examined together under a microscope and the dimensional change is recorded. The dimensions of the square sample are accurately measured prior to heat treatment using a Mitutoyo Quick Vision QV202 Pro (Pro) instrument, then heat treated at the appropriate time and temperature, and the sample dimensions are remeasured. Since the automatic optical instrument can measure several tens of times for each sample, a statistical method can be used to determine dimensional changes as small as 1 micron, which is less than 5-10 ppm of the sample size used. It corresponds to the dimensional change of. Using repeated heat treatments and measurements, the dimensional relaxation behavior of the glass can be determined at a certain temperature as a function of time.

  FIG. 1 shows the results of consolidation tests performed on a series of commercial and laboratory glasses to investigate the effect of strain point on consolidation. As can be seen from this figure, the change in consolidation at the strain point is a non-linear phenomenon, with the greatest improvement over the 20 ° C. range between 660 ° C. and 680 ° C. In this regard, it is noted that 660 ° C. is a typical strain point for AMLCD glasses currently on the market. By increasing the strain point to just 20 ° C. and 680 ° C., the consolidation drops to 70 ppm to less than 30 ppm. That is, the improvement exceeds 50%. This improvement is sufficient for some poly-Si processes. For other processes, further improvements may be required. As shown in FIG. 1, when the strain point is increased from 660 ° C. by 50 to 100 ° C. or more, a consolidation level of 20 ppm or less is obtained. These levels are suitable for poly-Si processes currently in use or expected to be used within a few years.

  FIG. 2 shows the effect of repeated heat treatment on glass having different strain points. The repeated heat treatment is more accurately mimicking the poly-Si manufacturing process, rather than the single heat treatment used to generate the data of FIG. For FIG. 2, each of the three glasses, glass A corresponding to Example 68 in Table 1, Glass B corresponding to Example 65 in Table 1, and Glass C, which is Corning Eagle 2000F glass. The sample was inserted into a furnace at 600 ° C., and the temperature was increased and maintained at that temperature while continuing the experiment. For the first heat treatment, the time was 5 minutes, the second time was another 5 minutes (total time was 10 minutes), etc. As shown in Table 2, the last four times were 60 minutes each. . After each heat treatment, the glass sample was removed from the furnace and placed between two fans and quenched. In this way, the glass sample was basically subjected to a temperature step change.

  As can be seen from FIG. 2, for all three samples, consolidation per test time decreases with increasing time. This is because the glass structure is relaxed based on it before it is subjected to a 600 ° C. treatment. However, glasses with high strain points, ie, glasses A and B of the present invention, showed significantly lower levels of consolidation than glass C, which has the strain point characteristics of currently available AMLCD glasses. The data plotted in FIG.

  In addition to the low pressure density, the glass must meet strict forming requirements applicable to fusion draw or related processes. Devitrification is initially defined as the formation of a crystalline phase from homogeneous glass. The maximum temperature at which crystals coexist with glass is defined as the liquidus temperature. As will be described later with respect to the glass test in Table 1, the liquidus temperature is measured by placing a crushed glass sample in a platinum boat and heating in a tube furnace with a gradient of 10 ° C. or less per cm for 24 hours. . The viscosity of the glass at the liquidus temperature is called the liquidus viscosity. A precise sheet glass forming process usually requires a relatively high liquidus viscosity, for example, greater than 40,000 poise, preferably greater than 85,000 poise.

  Glass must also meet stringent melting requirements for manufacturing purposes. The temperature at which the glass batch components melt in an economically reasonable time and the temperature at which trapped bubbles escape from the glass in a reasonable time typically corresponds to a viscosity of about 200 poise. Due to the durable high melting point or high temperature in precious metal containers, at a temperature of about 1,680 ° C., 200 poise is the actual upper limit. By changing the batch material from what was previously used, more viscous glasses can be melted with proportionally higher viscosities, but with such materials the costs are extraordinary and the glass is melted and adjusted to a higher viscosity system It is technically very difficult to transport it with A number of glass compositions are shown in Table 1 along with their physical properties.

The glass properties shown in Table 1 were determined according to conventional techniques in the glass industry. Thus, the coefficient of linear thermal expansion (CTE) over a temperature range of 25 to 300 ° C. is represented by × 10 ⁻⁷ / ° C., and the strain point is represented by ° C. These were determined from fiber elongation techniques (references ASTM E228-85 and C336, respectively).

The density in grams / cm ³ was measured by the Archimedes method (ASTM C693).

  The melting point at 0 C (defined as the temperature at which the glass melt exhibits a viscosity of 200 poise) was calculated using the Fulcher equation fitted to high temperature viscosity data measured by a rotating cylinder viscometer (ASTM C965-81).

The liquidus temperature of the glass at ° C. was measured using the standard gradient boat liquidus method of ASTM C829-81. This is done by placing the crushed glass particles in a platinum boat, placing the boat in a furnace with a gradient temperature range, heating the boat in the appropriate temperature range for 24 hours, and examining the maximum temperature at which crystals appear inside the glass by a microscope. It is included by seeking. More specifically, the glass sample is removed from the Pt boat in a single piece and examined using a polarizing microscope to identify the location and nature of the crystals formed against the Pt and air interface and the interior of the sample. Since the furnace gradient is known, the temperature versus location can be well estimated within 5-10 ° C. The temperature at which crystals are observed at the inner point of the sample represents the liquidus of the glass (for the corresponding test time). The test may be performed for a long time (eg, 72 hours) to observe the slow growing phase. The crystal phases of the various glasses in Table 1 are described in the following abbreviations. anor-- anorthite, calcium aluminosilicate mineral, Cris-- cristobalite _(SiO 2), _cels-- mixed alkaline earth celsian, Sr / Alsil-- strontium aluminosilicate phase, SrSi-- strontium silicate phase. The liquidus viscosity at Poise was determined from the liquidus temperature and the Fulcher equation.

  The value of Young's modulus in Gpa was determined using a general type resonance ultrasonic spectroscopy technique described in ASTM E1875-00e1.

As can be seen from Table 1, Examples 1-88 have values for density, CTE, strain point and Young's modulus that make the glass suitable for display applications such as AMLCD applications. Although not shown in Table 1, the glass also has chemical durability suitable for these applications. In particular, Examples 68, 69, 70 and 71 are each 10 wt. % HF was found to have a weight loss of 6.7-7.5 milligrams / cm ² when soaked at room temperature for 20 minutes. By way of comparison, commercially available AMLCD glasses exhibit a weight loss of 5-8 milligrams / cm ² when tested in this manner. All of the example glasses can be formed using a downdraw technique such as a fusion technique. Thus, it has a liquidus temperature of 1250 ° C. or lower, a liquidus viscosity of 85,000 poise or more, and in many cases 150,000 poise or more.

  Glasses having the compositions and properties shown in Examples 71 and 79 are currently considered to represent the most preferred embodiments of the present invention, i.e., at the present time giving the best combination of properties for the purposes of the present invention.

  Throughout this application, various references are referenced. The entire disclosures of these documents are hereby incorporated by reference into the present application to more fully describe the compounds, compositions and methods described herein.

  Various modifications and variations can be made to the materials, methods, and articles described herein. Other aspects of the materials, methods, and articles described herein will be apparent in light of the specification and practice of the materials, methods, and articles disclosed herein. Specifications and examples are to be considered illustrative.

Claims (7)

Mole percent on oxide basis,
SiO ₂ 64.0-72.0
Al ₂ O ₃ 9.0-16.0
B ₂ O ₃ 1.0-5.0
MgO ₊ La ₂ O 3 1.0-7.5
CaO 2.0-7.5
BaO 1.0-7.0
SrO 0.0-3.5
Including
here,
(1) Σ (MgO + CaO + SrO + BaO) / (Al ₂ O ₃ ) ≦ 1.50, where Al ₂ O ₃ , MgO, CaO, SrO, BaO represents the mole percentage of each oxide component,
(2) When the content of SrO is not 0 mole percent, the BaO / SrO ratio in mole percent is 2.0 or more,
(3) The amount of any oxide other than SiO ₂ , Al ₂ O ₃ , B ₂ O ₃ , MgO, CaO, BaO, SrO, La ₂ O ₃ is 2.0 mole percent or less,
(4) The contents of As ₂ O ₃ and Sb ₂ O ₃ are each 0.005 mole percent or less,
(5) having a strain point of 700 ° C. or higher,
(6) exhibit a dimensional change of less than 30 ppm for a heat treatment at 600 ° C. for 5 minutes,
Glass without alkali.   A liquid crystal display substrate comprising the glass according to claim 1.   The glass according to claim 1, having a liquidus viscosity of 150,000 poise or more. A method for producing a glass sheet not containing alkali by a downdraw method,
Selecting, melting and clarifying batch materials such that the glass constituting the glass sheet has the composition of claim 1,
The average gas content level of an assembly of 50 consecutive glass sheets produced from the molten and clarified batch material by the downdraw method is less than 0.10 gas content / cubic centimeter, A method for producing an alkali-free glass sheet having a volume of at least 500 cubic centimeters.   The method according to claim 4, wherein the downdraw method is a fusion draw method.   6. The method according to claim 4, further comprising using the glass sheet as a substrate for a liquid crystal display.   The method according to claim 4, 5 or 6, wherein the glass constituting the glass sheet has a liquidus viscosity of 150,000 poise or more.

Images